A conventional hot water generator is disclosed in JP-A No. 2002-130821. In this device, the hot water withdrawal pipe and cold water intake pipe of a heat exchanger are connected through a circulating pipe having a circulating pump and when withdrawal of hot water is stopped, the circulating pump forces hot water in the heat exchanger to circulate through the hot water withdrawal pipe, circulating pipe and cold water intake pipe back to the heat exchanger. When withdrawal of hot water is stopped, the circulating pump forces hot water in the heat exchanger to circulate through the hot water withdrawal pipe, circulating pipe and cold water intake pipe back to the heat exchanger to prevent hot water from staying in the heat exchanger so that hot water does not rise above a preset temperature due to remaining steam in the heat exchanger.
However, the above conventional hot water generator has a drawback that when withdrawal of hot water is stopped, hot water in the heat exchanger is just forced to circulate through the hot water withdrawal pipe, circulating pipe and cold water intake pipe back to the heat exchanger by the circulating pump and thus the ability to prevent the hot water temperature from rising above a preset temperature is low and when withdrawal of hot water is restarted, a relatively high temperature water above the preset temperature may be withdrawn.